<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>欢迎注册</title>
    <link href="css/register.css" rel="stylesheet">
</head>
<body>

<div class="form-div">
    <div class="reg-content">
        <h1>欢迎注册</h1>
        <span>已有帐号？</span> <a href="login.html">登录</a>
    </div>
    <form id="reg-form" action="#" method="get">

        <table>

            <tr>
                <td>用户名</td>
                <td class="inputs">
                    <input name="username" type="text" id="username">
                    <br>
                    <span id="username_err" class="err_msg" style="display: none">用户名不太受欢迎</span>
                </td>

            </tr>

            <tr>
                <td>密码</td>
                <td class="inputs">
                    <input name="password" type="password" id="password">
                    <br>
                    <span id="password_err" class="err_msg" style="display: none">密码格式有误</span>
                </td>
            </tr>


            <tr>
                <td>验证码</td>
                <td class="inputs">
                    <input name="checkCode" type="text" id="checkCode">
                    <img src="imgs/a.jpg">
                    <a href="#" id="changeImg">看不清？</a>
                </td>
            </tr>

        </table>

        <div class="buttons">
            <input value="注 册" type="submit" id="reg_btn">
        </div>
        <br class="clear">
    </form>

</div>

<script>
    // 给用户名输入框绑定，失去焦点的事件
    document.getElementById("username").onblur = function() {

        // 获取用户名的值
        var username = this.value;



        // 发送 Ajax 请求


        // 创建核心对象
        const xhttp = new XMLHttpRequest();
        // 发送请求
        xhttp.open("GET", "http://localhost:8080/brand-demo/ajaxServlet?username=" + username, true);
        xhttp.send();
        // 获取响应
        xhttp.onreadystatechange = function() {
            if (this.readyState == 4 && this.status == 200) {
                // alert(this.responseText);
                if(this.responseText == "true") {
                    // 用户名存在,显示提示
                    document.getElementById("username_err").style.display = '';
                } else {
                    // 用户名不存在,清除提示
                    document.getElementById("username_err").style.display = 'none';
                }
            }
        };
    }
</script>

</body>
</html>